SU1486900A1 - Method of determining value of elastic mechanical stresses in ferromagnetic materials - Google Patents

Description

The invention relates to measuring technique and can be used for non-destructive determination of the magnitude and sign of mechanical stresses in ferromagnetic materials. Purpose of the invention 2

improving the accuracy of determination by detuning from the influence of changes in the structure of the material — achieved by reversing the product in four pairwise perpendicular directions with an attached electromagnet, of which one pair is directed along the main stresses and the other at any angle to the first. Using the results of four measurements and a calibration curve, the method of successive approximations using the microprocessor to calculate the true values of the main voltages. In parallel, a signal component characterizing structural C is calculated.

deviations of the controlled material. .

In the permanent storage device I / pre-entered data from the graph 1 ^ curve curves for several I *

controlled materials. 2 Il. _but

The invention relates to measuring technique and can -. be used for non-destructive determination of the magnitude and sign of mechanical stresses in ferromagnetic materials, for example, in their surface layers, as well as the structure of ferromagnetic materials.

The purpose of the invention is to improve the accuracy of determination by detuning from the influence of changes in the structure of the material.

Figure 1 shows the functional diagram of the device for implementing the method; figure 2 is a calibration graph of the dependence of the signal components on the stress ΰ for steel 20 for

magnetization reversal frequency 200 Hz, amplitude of the sinusoidal magnetization reversal field Yu ^ A / m, frequency analysis of magnetic noise 70 kHz.

The device contains an attached electromagnet with magnetic core 2 and magnetizing winding 3 mounted on controlled material 1, alternator 4, mechanism 5 of turning an electromagnet around axis 0 perpendicular to the surface of material 1, and limb 6. Registration and processing of the flow of electromotive force from jumps at 1486900 A1

3

• 1486900

four

magnetization is performed by series-connected induction measuring coil 7, wideband amplifier 8, filter 9, analog-to-digital converter (ADC) 10, special signal processor 11 and indicator 12, Another input of processor 11 is connected to the output of a programmable storage device (ROM) 13, and the second output - to the input of the device 14 control (CU) operation of the ADC.

The method is as follows.

The method is based on the well-known rule of resistance of materials, according to which, in a plane stress state, the sum of principal stresses is equal to the sum of two mutually perpendicular stresses C and Cβ directed at any angles & and β to the main ones:

σ, + St _g = + σ _β . (ΐ)

The main stages of the implementation of the computational algorithm are as follows:

Changing the direction of the magnetization reversal field, they find the directions in which the signals V, and respectively the maximum and minimum, and measure Y ₍ and V _g .

We take the first approximation of the component (ήν ') ^ of the signal, due to the structure of the material.

The value of the signals and Ϋβ are measured at an angle of 45 ° to the main directions.

Calculate the components of these signals, due to voltage: θ £), = ν ^ - αν ^ε ) ,; (2)

(^), ^{= ν} β "· < ³ )

According to the graph of the dependence of the signal component on the stress ΰ (for the initial structural state of the material), the first approximations of the stress values ((7,) ^, (θΐ \> ((? (<),, (<3р), with their signs) are determined.

Check them according to equation (1). If it is not fulfilled, then change the value of (yU ^s ), · to the second approximation (yU) _nd and repeat all computational operations until the misclosure between the left and right sides of equation (1) becomes less than a predetermined value?

A device that implements the proposed method works as follows.

The coil 7 register the magnetization jumps arising in the flat-stress controlled material 1, which is re-magnetized by the attachment magnetic circuit 2, installed in series in positions A, B, C, D, by means of a mechanism. 5 with indicators and a limbus 6. With the four positions indicated, the coil-registered magneto 7 magnetization jumps are amplified by a wide-band amplifier 8 and using the filter 9 of them the specified spectral components are distinguished. Signals proportional to the magnitude of the spectral plane of magnetic noise are converted into digital code using an ADC. The digitized signals are fed to the input of a special processor 11, which is programmed to average the result of samples of one dimension and the implementation of the computational algorithm written above. In addition, the processor 11 sends commands to the control unit, which controls the ADC input in such a way that the accumulation of the results of a sample of one measurement occurs at one position of the magnetic circuit 2. The other input of the processor 11 is connected to the output of the ROM, into the memory of which the calibration curve is pre-entered in coded form or table) of the type of curve shown in FIG. 2 for steel 20. The result of processing four signals in accordance with the described algorithm is indicated by the indicator 12 directly in the magnitude of the voltages. In addition, the display indicator 12 indicates the value that characterizes

<structural state of the controlled material.

Claims (1)

Claim The method of determining the magnitude of elastic mechanical stresses in ferromagnetic materials, which consists in the reversal of the material surface in succession in two mutually perpendicular directions along the directions of the main stresses, recording and measuring the vapor5 1486900 6 EMF meters from magnetization jumps, which are used to determine the magnitude of elastic stresses, differing from the fact that, in order to improve the accuracy of determination by detuning from the influence of changes in the structure of the material, the surface of the material is additionally remagnetized in two other mutually perpendicular directions, and I register EMF is measured from magnetization jumps during magnetic reversal in these directions, and the voltages determine _g by the method of successive approximations e using the results of four measurements and the dependences of the parameters of the EMF of magnetization jumps on the magnitude of the ten-point voltage in the corresponding four directions, obtained in advance on the sample. fzg.1 compressive tension ^ stretching 6> * / μ ** 11Τ * fae. 2